Pressurizing of wells by gaseous release



April 3, 1956 H. M. GREENE PRESSURIZING OF WELLS BY GASEOUS RELEASE Filed Feb. 24. 1953 INVENTOR.

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United States Patent PRESSURIZING F WELLS BY GASEOUS RELEASE Haskell M. Greene, Whittier, Calif.

Application February 24, 1953, Serial No. 338,373

18 Claims. (Cl. 166-63) This invention relates to improved apparatus for expelling treating materials within an oil well, as for in stance for the purpose of increasing the rate of production of the well. ln certain respects, the apparatus of the present invention is an improvement on that shown in my co-pending applications Ser. No. 161,986, filed May 15, 1950 on Oil Well Cementing Packer and Ser. No. 331,973, filed January 19, 1953 on Apparatus for Firing Propellent Charges in Wells, now Patent Nos. 2,696,258 and 2,696,259 respectively.

As is well known, the rate of production of an oil well is often decreased by accumulation of wax, paraiiin and the like within the pores of the earth formation. An important object of the present invention is to provide improved means for cleaning such materials from the earth pores, to thus open the formation for increased oil ow into the well. This is achieved by forcing Huid under extremely high pressure from the well and laterally into the surrounding formation. The pressure is created by gasifying in the well a gas producing or propellent charge, i. e. an explosive or combustible charge, or a cartridge of liquid carbon dioxide or other normally gaseous fluid under high pressure.

Of particular importance to the present invention is the manner in which the force of the propellent gases is conlined or localized, to assure application of the gas pressure at a desired zone and thus cause the formation cleaning fluid to penetrate very deeply into the formation. Specifically, such deep penetration is effected by closing olf the well bore at a location above the propellent gases, so that the gas force can not be dissipated upwardly within the well, and is directed undiminished into the formation. For thus closing off' the well bore, I preferably employ a packer which is adapted to be expanded outwardly against the bore wall by the force of the gases themselves. Also, 1 may employ a second packer spaced beneath the first, and acting with the upper packer to effectively localize the gas force at a desired zone in the well. This second packer, like the first, may be of a type to be expanded against the bore wall by the force of the gases.

The fluid forced into the formation may comprise merely the propellant gases themselves, in which case the temperature and pressure of the gases act to melt and then clean out any waxes, etc., which may have accumulated in the formation. To supplement the effect of the gases, a cleaning liquid may be carried by the apparatus at a location to be forced into the Well by the gases. This liquid may be contained within a chamber having lateral openings initially closed by closures adapted to be opened by the force of the gases upon firing of the propellent charge. The cleaning liquid may be a suitable solvent or acid adapted to facilitate cleaning of the formation. lt is also contemplated that certain other materials, such as cement for example, may in certain instances be deposited in the well by apparatus embodying the invention. The apparatus may includel a gas gun within which the propellent charge is conit tained, and which is adapted to direct the gases against the liquid or other material to be dispensed.

1n order to assure effective clearing of the formation, I employ a gas producing charge which is capable of producing a very large quantity of gases. Preferably, the charge is so selected as to produce a quantity of gases which would occupy a space of at least about 9000 cu. ft. at atmospheric pressure.

The above and other features and objects of the present invention will be better understood from the following detailed description of the typical embodiments illustrated in the accompanying drawing, in which:

Figs. l, 2, 3 and 4 illustrate four different forms of apparatus for performing a well treating operation in accordance with the present invention.

Fig. 1 shows the production Zone of an oil well within which is positioned the usual perforated production liner 10. As will be understood, when the well is producing, oil flows through apertures 11 in liner 10 from the earth formation 12 surrounding the liner and into the interior of the well, to be taken upwardly through a conventional production string (not shown). At 13, I show a tool which is designed to open or clean the oil passing pores within formation 12, when the formation has become partially or completely closed to fluid ow as a result of the accumulation of paraiiin, waxes, or the like therein.

Liner 10 is connected to the lower end of the usual well casing 11i?. A seal of some type is desirably provided about casing to positively prevent the escape of formation cleaning gases upwardly about the casing during a cleaning operation. As a typical type of seal for this purpose, I show at 113 an annular body of cement which completely closes off any gas leakage space between the liner and formation.

Tool 13 includes a vertically extending cylindrical body 14, which may be suspended in the well by a bail 15 connected to a wire suspension cable 16. Body 14 carries a downwardly directed gas gun 17 within which may be positioned a gas producing charge 1S (i. e. an explosive or combustible charge, or a cartridge of carbon dioxide or the like under high pressure). This charge is adapted upon firing to produce large volumes of gases, which expand downwardly through the open lower end of the body 14 and outwardly into the formation.

About body 14 is carried a tubular vertically extending resiliently expansible packer element 30, typically formed of rubber, whose upper and lower ends are annularly clamped inwardly against the wall of body 14 by a pair of circular straps 31. Packer Sil normally tends to retract radially inwardly to a position of vertically and cir- V cularly continuous contact with the Wall of body 14, but

is resiliently expansible radially outwardly into engagement with liner 10 by the force of the propellent gases upon firing. When thus expanded (to the position of Fig. l), packer 3l) forms a tight annular seal with liner 10, to positively close off the Well bore against upward dissipation of the forces of the propellent gases. To communicate the pressure of the gases to the inside of packer 30, for expanding the packer against the bore wall, the upper portion of tubular body 14 contains a number of apertures 32, through which the gases may flow through the wall of the body and into contact with the packer. Preferably, the lowermost of these apertures is at least as high as, and preferably higher than, the lower end of gas gun 17 (in its upwardly recoiled position) to require a somewhat circuitous gas flow to the packer. When the gases thus must reverse their downward course and ow upwardly in order to reach the packer, the danger of rupturing the packer by the force of the gases is minimized.

The gas gun may form a cylindricalpvertically extend-` ing` chamber closed at its upper end, and having side and top walls of a strength to withstand the force of the propellent gases upon tiring. Charge 18 may be retained within this downwardly opening cylindrical chamber in any suitable manner. The propellent charge may contain an electrically ignited fuse 19 at its lower end, to which igniting electricity is conducted from a battery 20 at the surface of the earth under the control of a switch Z1. One side of battery 20 is connected to fuse 19 through an electric wire 22 extending downwardly within the well alongside suspending cable 16, and connecting to an insulated electric terminal 23, which is suitably connected to the fuse. The second side of battery 20 is connected to the fuse through the metal body 14, bail 1.5 and cable 16, all of which are grounded.

Gas gun i7 is mounted within body 14 of the tool by means of an annular bushing 24, which is threadedly connected into the upper end of the body. The gas gun is preferably guided by bushing 24 for limited upward recoiling movement upon tiring of the charge 18. For this purpose, bushing 24 may have a radially inwardly projecting portion 29 having an inner bore 25 within which an upper portion 26 of the gas gun is slidably movable. Above and beneath its bushing engaging portion 26, the gas gun has a pair of upper and lower increased diameter ange portions 27 and 28, which are engageable with the inwardly projecting portion 29 of the bushing to limit its vertical movement. Normally, gun 17 falls by gravity to its lowermost position, in which upper ange 27 engages the upper side of portion 29 of the bushing. Upon Vtiring, the force of the produced gases causes the gun to recoil upwardly to its Fig. l position in which lower ilange 2S engages the underside of the bushing.

ln treating a well with the apparatus of Fig. l, the device is rst lowered to the production zone of the well, and switch 21 is then closed to re propellent charge 1S. Ignition of the propellent creates a large volume of high pressure and high temperature gases, which are directed downwardly through the open lower end of body 14 by gas gun 17. The initial increase of pressure within body 14 acts to expand packer 30 against the bore wall to positively close ol the bore above the gases and thus prevent upward dissipation of the force of the gases. Of course, the initial force of the gases also causes the gas gun to recoil upwardly to its Fig. l position.

As the gases ow downwardly from body 14, their extremely high pressure causes them to leave the well through apertures 11, and penetrate laterally and very deeply into the surrounding earth formation 12. The temperature and pressure of the gases are such as to melt any accumulated waxes, paran, and the like within the fromation, and force these materials from within the pores of the formation, to thus clean out the pores and provide for very free ow of oil from the formation and into the well. It has been found that treatment of the well in this manner often has the effect of cleaning the formation for a distance of severalhundred feet from the well bore, and usually vastly increases the rate of production of the well.

In order to assure a most effective penetration of the gases into the formation, the propellent charge 18 is so selected as to produce gases in very large quantity, and preferably over a relatively long period of time. As previously mentioned, the quantity of gases produced is desirably such as would occupy a space of at least about 9000 cu. ft. at atmospheric pressure (14Q7 p. s. i.).

In accordance with the teaching of my copending appli cation Ser. No. 331,973 on Apparatus for Firing Propellent Charges in Wells, the charge 18 is desirably adapted upon ignition to generate gases over a period betweenahout 11/2 and 3.0 seconds, under the pressure conditions existing at the production zone of the well. The propellent, may also. be so selected as tov produce considerablygreater volumes of. gases per dram of. propellent than are produced? by many commonl propellents, the propellent having a capacity for producing between about 1.00. and 40.0 en.. it. Gigas. at atmospheric .pressurefrom each dram of propellent. The burning speed of the propellent or powder may be between about .2 of an inch and 5 inches per second.

A typical gas generating material may comprise a mixture of nitroglycerine, or smokeless powder, and nitrocellulose, the mixture being pressed into solid or stick form. Generally speaking, the nitroglycerine content may range between 50% to 90%, an increase in the amount of nitrocellulose having the effect of retarding the burning speed. It is found desirable to govern the burning speed by controlling the nitroglycerine to nitr0- cellulose ratio and. also by venting or perforatin g the solid stick charge along its length. lt is estimated that the charge will develop pressures upwards of 20,000 pounds per square inch and it has been observed that the burning speed remains adequately constant, and below any explosive rate, under pressures exceeding 10,000 pounds per square inch.

The quantity of charge used will depend upon the size and depth of the bore hole or casing and upon the length of the formation to be penetrated or purged. A minimumlength of bore hole to be cleared may be regarded as around 5 feet and as requiring a charge having the stated composition and of at least about 5 ounces. Such a charge is capable of producing about 1800-2000 cu. it. of gases (at atmospheric pressure) per ounce, so that the total gas production is at least about 9000 cu. ft. (at atmospheric pressure). Probably the maximum length of formation and'hole to be treated in one operation will be around 30 feet. The quantity of charge of the above composition may be stated generally to range between about 5 ounces and 400 ounces.

Many instances will be encountered where the vertical extent ofthe zone to be cleared will range in excess of 30 feet. In those instances vthe procedure will be to pack olf and treat successive lengths of the hole, e. g. in intervals of` 5 to 30 feet, until the entire extent of the stratum is treated.

It is also contemplated that carbon dioxide either alone or together with a heating medium, may be used as the propellent. Whether carbon dioxide alone lcan be used depends upon the well temperatures. The practice would be to lower an elongated pressure capsule containing liquefied carbon dioxide and to explosively rupture the capsule to release the carbon dioxide. Probably where any considerable quantity of carbon dioxide is used (incidentally the amount of carbon dioxide may be stated to be between about 50 ounces to 400 ounces) the heat content of the well in the treating zone will not be sufcient for the desired carbon dioxide vaporization and expansion. Accordingly to supply supplementary heat, the carbon dioxide capsule, for example, may be enclosed within a sheath of nitroglycerine-nitrocellulose, the burning ofwhich may actto openv the carbon dioxide capsule.

Fig. 2 shows a second form of apparatus embodying the invention, which apparatus is identical with that of Fig. l except for the provision of a body of well cleaning liquid 33 within its lower end. For containing liquid 33, body 14a of the Fig. 2 device extends downwardly a considerable-distance beneath packer 30a, to form a bottom liquid containing chamber closed atv its lower end by a bottom wall or plug 34. Beneath the lower end of packer 30a, the wall of body 14a contains a number of apertures 35 through which liquid 33 may be discharged laterally from the body and into the earth formation. These apertures are. initially closed by closures 36 which retain the liquid within the body during lowering of the tool into the well, but are preformed to rupture or open under the force ofi the .gases .produced by ignition of propellent charge 18a, to allow lateral discharge of the' liquid. Closures 36 may' typically be formed of aru'pturable cement', plastic material, or thelike.

The liquid 33 is desirably of a free owing consistency,

andere and comprises a cleaning liquid adapted to flow into and clean the pores ofthe earth formation. This liquid preferably comprises a suitable well cleaning acid, such as hydrochloric acid or a suitable solvent, such as a light hydrocarbon distillate, or any of the various known types of chlorinated organic solvents.

The tool of Fig. 2 is lowered into the well and red in the same manner as that of Fig. 1. The initial force of the gases produced by the charge 18a expands packer 30a against the bore wall, to close off the bore wall against upward dissipation of the gas force. The pressure of the gases then ruptures closures 36, and forces liquid 33 laterally from the body through apertures 35, then through liner apertures 11 and far into the surrounding earth formation 12a. The liquid 33 acts to dissolve waxes, parain, and the like, and together with the high temperature and high pressure gases effectively opens the pores of the formation.

The apparatus of Fig. 3 is substantially the same as that of Fig. 2, except that body 14b of the device extends downwardly beneath the location of its plugged liquid escape apertures 35b, and at its lower end carries a second resiliently expansible tubular packer 37. This packer may be substantially identical with the upper packer 181;, being clamped at its upper and lower ends 38 and 39 against the wall of body 14b, and being expansible against the bore wall by fluid pressure communicated through body apertures 40. The lowerend of body 14b in Fig. 3 may be closed in any suitable manner, as by a bottom cap 34b.

In using the Fig. 3 device, a body of liquid 33b corresponding to that shown at 33 in Fig. 2 is lled into body 1417 to approximately the level shown. Upon tiring of a propellent charge within gas gun 17b, the generated gases act to expand vertically spaced packers 18h and 37 against the bore wall, in a manner such that liquid discharging from the body through apertures 35h is confined to a limited zone of the well. The gas force for expanding lower packer 37 is of course communicated to that packer through the liquid 33b. After the packers have expanded, closures 36h open, to allow escape of the liquid from the body and into the surrounding earth formation. The deep penetration of the liquid and filling gases acts to open the formation in the manner discusse in connection with Fig. 2.

Fig. 4 is a dual packer arrangement similar to that shown at Fig. 3 but differs in that a different type of packer 37C is employed at the lower end of the tool. Speciticially, packer 37C comprises merely an upwardly directed and flaring cup formed of rubber or other resilient sealing material, and fastened to the lower cap 34e of the device by a bolt 41. The tiring pressure acts against packer cup 37C at the outside of body 14e, and has the effect of expanding the cup against the liner c to form the lower pressure retaining seal. Except for the manner of expansion of the lower packer, the functioning of the Fig. 4 apparatus is the same as that of Fig. 3.

The gas producing charges in Figs. 2, 3 and 4 desirably have the same burning and gas producing characteristics as were described in detail in connection with the charge 1S of Fig. 1.

I claim:

l. Well treating apparatus comprising a body adapted to be lowered into a well, two packers carried by the body adapted to engage the well bore wall and seal the bore at two vertically spaced upper and lower locations against both upward and downward escape of gases from between said two locations, and a gas producing charge carried by the body and constructed to produce a large quantity of gases under high pressure vertically between the packers at a position to apply the force of said gases to the bore wall between said spaced locations.

2. Well treating apparatus as recited in claim 1, in which said body has a tubular portion having side wall apertures, one of said packers being a tubular resilient sleeve disposed about said tubular portion of the body and expansible against the bore wall by the force of gases from the charge communicated to the interior of the packer through said apertures.

3. Well treating apparatus as recited in claim 1, including a mass of well treating material contained within said body at a position to be displaced outwardly therefrom and against the formation by the force of said gases, and a gas gun containing said charge and carried by said body at a location to direct the gases against said material.

4. Well treating apparatus as recited in claim 3, in which both of said packers are adapted and positioned for expansion against the well bore wall by the force of said gases, said body forming a chamber containing said material and having side apertures through which the material is forced laterally against the formation, said apparatus including closures initially closing said apertures but openable by the force of said gases to allow escape of said material from the body.

5. Well treating apparatus as recited in claim 1, in which one of said packers is exposed to the force of said gases and is constructed for expansion against the well bore wall by said gas force.

6. Well treating apparatus as recited in claim l, including a mass of well treating material contained within said body at a position to be displaced outwardly therefrom by the force of said gases and against the formation between said packers.

7. Well treating aparatus as recited in claim 1, including a mass of well treating material contained within said body at a position to be displaced outwardlytherefrom by the force of said gases and against the formation between said packers, at least one of said packers being exposed to the force of said Vgases and being constructed for expansion against the well bore wall by saidgas force.

8. Well treating apparatus comprising a body adapted to be lowered into a `well and forming a verticallyv extending chamber for containing a mass of well treating material, said chamber having apertures in its side wall through which said material is dischargeable laterally against the surrounding formation, a gas producing propellent charge carried by said body adapted and positioned to produce a large quantity of high pressure gases at a location to force said material through said apertures and against the formation, closures initially closing said apertures and openable by the force of said gases to allow escape of said material, and a packer carried by said body and adapted to be urged outwardly against the bore wall at a loction bove said apertures and to thereby close the bore against upward dissipation of the force of said gases.

9. Well treating apparatus as recited in claim 8, in which said well treating material is a cleaning liquid adapted to be forced into the formation by said gases to clean the formation.

l0. Well treating apparatus as recited in claim 8, in which said well treating material is a cleaning liquid adapted to be forced into the formation by said gases, said body having an upper tubular portion above said chamber containing said charge and having side wall apertures, said packer being a resiliently expansible packer sleeve disposed about said upper portion of the body and expansible against the bore wall by gases communicated to the packer from said charge through said apertures in the upper portion of the body, there being a downwardly opening gun in said upper portion of the body containing said charge and directing gases downwardly toward said cleaning liquid.

ll. Well treating appartus comprising a body adapted to be lowered into a well and forming a chamber, a body of well cleaning liquid contained in said chamber, a gas producing charge carried by the body and adapted and positioned to ,force said liquid from the chamber and deeply into. the surrounding formation, and a packer carfied by said body and adapted t engage the bore wall and form a seal closing the bore against upward dissipation of the gas force.

l2. Well treating apparatus as. recited in claim 11, in which said packer is exposed to the force of the gases produced by said charge and is constructed for expansion against the well bore wall by said gas force.

13. Well treating apparatus as recited in claim 11, in which said body has an upper tubular portion above said chamber containing said charge and having side Wall apertures, s'aid packer being a resiliently expansible packer sleeve disposed about said upper tubular portion of the body and expansible against the bore wall by the force of gass from said charge communicated to the interior of the sleeve through said apertures.

14. Well treating apparatus comprising a body adapted to be lowered into a well, a charge carried by the body adapted to produce in the well large quantities of gases under high pressure, and a packer carried by said body and adapted t0 @usage the bore wall aud-form a seal closing, the bore against upward dissipation of the gas force, said body being of an essentially open construction providing a gas path from said charge to the bore wall which is open to passage of substantially all of said gases without substantial restriction into the formation surrounding the well to penetrate and clean the formation.

15. Well treating apparatus as recited in claim 14, in which said packer is exposed to the force of said gases and is constructed to be expanded against the well bore wall by said gas force.

1,6, Well treating apparatus as recited in clairn 14, in which said body is tubular and extends vertically and coniains saisi shares, said body having a bottom Opening through which the gases are openly discharged Without substantial restriction into the well, said packer being resilient and tubular and disposed about said body, said body containing wall apertures placing the interior of the bodyin communication with the inner side of the packer.

17V Well treating apparatus as recited in claim 16, including a downwardlyY opening gun in said body containing said charge and directing the gases downwardly through said bottom opening of the body.

18. Well treating apparatus comprising a body adapted to be lowered into a well, two packers-carried by the body aadpted to engage the well bore wall and close the bore at two vertically spaced locations, and a gas producing charge carried by the body and constructed to produce a large quantity of gases vertically between the packers at a location to apply the force of said gases to the bore wall between said locations, said body being tubular and having upper and lower tubular portions at said spaced locations containing wall apertures, said packers being two resilient tubular sleeves about said upper and lower portions of the body respectively and expansible against the bore wall by the force of said gases communicated to the packers through said apertures, a rnass of well treating liquid contained in` said tubular body and at least partially locatedl vertically between the locations of said packers, there being outlet means in the wall of said body vertically between the packer locations through which said liquid is forced outwardly by the gases to penetrate the formation, and a gas gun in the body above said liquid containing said charge and directing the gases therefrom downwardly toward the liquid.

References Cited inthe le of this patent UNITED STATES PATENTS 

1. WELL TREATING APPARATUS COMPRISING A BODY ADAPTED TO BE LOWERED INTO A WELL, TWO PACKERS CARRIED BY THE BODY ADAPTED TO ENGAGE THE WELL BORE WALL AND SEAL THE BORE AT TWO VERTICALLY SPACED UPPER AND LOWER LOCATIONS AGAINST BOTH UPWARD AND DOWNWARD ESCAPE OF GASES FROM BETWEEN SAID TWO LOCATIONS, AND A GAS PRODUCING CHARGE CARRIED BY THE BODY AND CONSTRUCTED TO PRODUCE A LARGE QUANTITY OF GASES UNDER HIGH PRESSURE VERTICALLY BETWEEN THE PACKERS AT A POSITION TO APPLY THE FORCE OF SAID GASES TO THE BORE WALL BETWEEN SAID SPACED LOCATIONS. 